1. Field of the Invention
The present invention relates to a network session control system for establishing a network session to execute voice communication or data communication between network terminals, and particularly relates to a network session control system that is capable of establishing a session at an appropriate timing while looking up the status of a user or a terminal.
2. Description of the Related Art
Along with the spread and decreasing cost of Internet technology, there is a significant trend towards services that had hitherto been performed using a dedicated protocol on dedicated lines being performed on an IP (Internet Protocol) network. Telephone services can also be performed on an IP network by a combination of voice communication on VoIP (Voice over IP) technology with H.323 and SIP (Session Initiation Protocol) designed as call control protocols. H.323 and SIP are not limited to telephone services and are designed to be usable in constructing and controlling sessions used for network services between terminals.
However, when H.323 and SIP are used, not to mention a telephone that uses conventional switching equipment, the method of utilizing these protocols in network services has hitherto generally involved attempting to establish a session using a terminal “when the caller/callee wishes to communicate.” Therefore, in the case of a telephone service, for example, when the callee is in conference and is unable to promptly respond, the callee usually either cannot be contacted, or could only do something to the effect of verbally asking for a return call. Drawbacks also frequently arise in that when a call eventually arrives from the callee, the original caller is then unable to respond, and other such cases in which a lengthy process is required in order to establish voice communication.
Conventional techniques for overcoming such drawbacks are proposed in JP-A7-264666 and 11-164361. The conventional technique described in JP-A 7-264666 is a reserved connection mobile communication system whereby a mobile device designated by an advance registration connects with a designated terminal upon reaching a designated area. Specifically, a mobile communication switching device is provided with a reserved connection registration processing device for storing reserved connection information in a home memory bank when the reserved connection that specifies the connection terminal, the mobile device, and the physical location of the mobile device has been registered from the terminal of a reserved connection registrant, and is also provided with a reserved connection control device for comparing the registered location with the designated area included in the reserved connection information when location registration is performed from the mobile device, and connecting the mobile device with the terminal designated in the reserved connection information when the registered location matches the designated area. An aspect is also disclosed in which a connection is established with the terminal of the reserved connection registrant by means of the reserved connection control device when the mobile device reaches the designated area, the message “The mobile device for which reserved connection registration is performed has reached the designated area. Connect?” is presented, and the mobile device is connected with the designated terminal only when a request to connect is made by the reserved connection registrant.
On the other hand, the conventional technique described in JP-A 11-164361 is a wireless communication system whereby monitoring and redialing are performed without burdening the transmission initiator until the mobile device is able to respond in a case in which the mobile device does not respond due to being out of area or for another reason. Specifically, when the transmission source terminal fails to call up the mobile device, a request is made to a service center to fill in for subsequent processing, the service center transmits to the mobile device a call setup signal in which a notice is written into a source sub-address of the call setup signal that a call has been received, a call setup signal is automatically transmitted to the transmission source terminal indicating a response to the incoming call at the source sub-address of the call setup signal when there is a call setup response from the mobile device, and the transmission source terminal that received this signal automatically calls the mobile device.
However, the above-described conventional techniques have drawbacks in that they consider only the terminal location and continuation of call processing, are not necessarily convenient for the user being called (a user of a mobile device in the case of JP-A 7-264666 and 11-164361), and have a high likelihood of not being able to smoothly establish a session. The conventional technique described in JP-A 7-264666 is configured so as to directly confirm availability to a pre-registrant when the mobile device reaches the designated area, or, in other words, when pre-conditions are satisfied, thereby smoothly establishing a session, but the session establishment procedure changes according to the relationship between the caller and the party being called, and there are many cases in which confirmation does not necessarily need to be obtained always from the party reserving the session. For example, the caller and the party being called are equals if their relationship to each other is that of coworker or friend, but the convenience of the customer in a customer-business relationship and the superior in a superior-subordinate relationship should be considered with priority.
The conventional technique described above also has the drawback of not reflecting the wishes of a user who does not wish to receive a reservation as such in the first place, because the reservation is received without considering the convenience of the user being called.